下列计算错误的是( )
A.(6a+1)(6a-1)=36a2-1 B.(-m-n)(m-n)=n2-m2
C.(a3-8)(-a3+8)=a9-64 D.(-a2+1)(-a2-1)=a4-1
计算(-4x-5y)(5y-4x)的结果是( )
A.16x2-25y2 B.25y2-16x2 C.-16x2-25y2 D.16x2+25y2
下列各式中,能用平方差公式计算的是( )
(1)(a-2b)(-a+2b); (2)(a-2b)(-a-2b);
(3)(a-2b)(a+2b); (4)(a-2b)(2a+b).
A.(1)(2) B.(2)(3) C.(3)(4) D.(1)(4)
计算:51×49=_________.
(1)(3a-4b)( )=9a2-16b2; (2)(4+2x)( )=16-4x2;
(3)(-7-x)( )=49-x2; (4)(-a-3b)(-3b+a)=_______.
下列计算对不对?若不对,请在横线上写出正确结果.
(1)(x-3)(x+3)=x2-3( ),__________;
(2)(2x-3)(2x+3)=2x2-9( ),_________;
(3)(-x-3)(x-3)=x2-9( ),_________;
(4)(2xy-1)(2xy+1)=2xy2-1( ),________.